Encoder, a decoder and corresponding methods using compact mv storage

ABSTRACT

The disclosure provides a motion vector compression method, comprising: obtaining a temporal motion vector; determining a compressed motion vector using a binary representation of the temporal motion vector comprising an exponent part and/or a mantissa part, wherein the exponent part comprises N bits, the mantissa part comprises M bits, and wherein N is a non-negative integer and M is a positive integer; and performing a temporal motion vector prediction (TMVP) using the compressed motion vector.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.17/358,572, filed on Jun. 25, 2021, which is a continuation ofInternational Application No. PCT/RU2019/050260, filed on Dec. 27, 2019.which claims priority to U.S. provisional Application No. 62/786,343,filed on Dec. 29, 2018 and U.S. provisional Application No. 62/786,344,filed on Dec. 29, 2018. All of the afore-mentioned patent applicationsare hereby incorporated by reference in their entireties.

TECHNICAL FIELD

Embodiments of the present application generally relate to the field ofpicture processing and more particularly to a technique for reducingmemory capacity in storing motion vector information.

BACKGROUND

Video coding (video encoding and decoding) is used in a wide range ofdigital video applications, for example broadcast digital TV, videotransmission over internet and mobile networks, real-time conversationalapplications such as video chat, video conferencing, DVD and Blu-raydiscs, video content acquisition and editing systems, and camcorders ofsecurity applications.

The amount of video data needed to depict even a relatively short videocan be substantial, which may result in difficulties when the data is tobe streamed or otherwise communicated across a communications networkwith limited bandwidth capacity. Thus, video data is generallycompressed before being communicated across modern daytelecommunications networks. The size of a video could also be an issuewhen the video is stored on a storage device because memory resourcesmay be limited. Video compression devices often use software and/orhardware at the source to code the video data prior to transmission orstorage, thereby decreasing the quantity of data needed to representdigital video images. The compressed data is then received at thedestination by a video decompression device that decodes the video data.With limited network resources and ever increasing demands of highervideo quality, improved compression and decompression techniques thatimprove compression ratio with little to no sacrifice in picture qualityare desirable.

SUMMARY OF THE DISCLOSURE

The purpose of this disclosure is to provide a solution to the problemof reducing memory capacity in storing information for deriving atemporal motion vector prediction while keeping the motion vectorrepresentation and precision in reasonable range.

This problem is solved according to the disclosure by providing a motionvector compression method, comprising: obtaining a temporal motionvector; determining a compressed motion vector using a binaryrepresentation of the temporal motion vector comprising an exponent partand/or a mantissa part, wherein the exponent part comprises N bits, themantissa part comprises M bits, and wherein N is a non-negative integerand M is a positive integer; and performing a temporal motion vectorprediction (TMVP) using the compressed motion vector.

In an embodiment, a operation of performing at least one bit shiftoperation based on the exponent part or the mantissa part of thetemporal motion vector to obtain a compressed motion vector may beapplied.

In another embodiment, the exponent part may correspond to the mostsignificant bit(s) (MSB) of the binary representation and the mantissapart may correspond to the least significant bit(s) (LSB) of the binaryrepresentation; or, the exponent part may correspond to LSB of thebinary representation and the mantissa part may correspond to MSB of thebinary representation.

Additionally, when the exponent part corresponds to MSB of the binaryrepresentation and the mantissa part corresponds to LSB of the binaryrepresentation, a value of the compressed motion vector may be derivedby the following operations: deriving a first shift value by applying aright shift of M bit to the binary representation; deriving last M bitof the binary representation as a first basic binary representation; andderiving the value of the compressed motion vector by applying a leftshift of the first shift value bit to the first basic binaryrepresentation.

Alternatively, when the exponent part corresponds to LSB of the binaryrepresentation and the mantissa part corresponds to MSB of the binaryrepresentation, the value of the motion vector component may be derivedby the following operations: deriving last N bit of the binaryrepresentation as a second shift value; deriving a second basic binaryrepresentation by applying a right shift of N bit to the binaryrepresentation; and deriving the value of the compressed motion vectorby applying a left shift of the second shift value bit to the secondbasic binary representation.

According to an embodiment, the temporal motion vector may comprise amotion vector horizontal component and a motion vector verticalcomponent.

According to another embodiment, the motion vector compression methodmay comprise: coding a first indicator, wherein the first indicator isused to indicate whether the temporal motion vector is compressedaccording to the motion vector compression method according to thedisclosure.

The motion vector compression method may comprise determining a value ofN.

Further, determining the value of N may comprises: coding the value ofN; or setting a predetermined value as the value of N; or deriving thevalue of N based on a resolution of a picture unit, wherein the pictureunit comprises a picture or a tile set; or deriving the value of N basedon a size of coding tree unit (CTU) or coding unit (CU).

More particularly, deriving the value of N based on the resolution ofthe picture unit may comprise: setting the value of N as 0, when thewidth of the picture unit is smaller than a first threshold and theheight of the picture unit is smaller than the first threshold; or,coding a second indicator to represent the value of N, when the width ofthe picture unit is smaller than a second threshold and the height ofthe picture unit is smaller than the second threshold; or, coding athird indicator to represent the value of N.

The second indicator may be binarized by a bit, and the third indicatormay be binarized by two bits.

In an embodiment, the first indicator, the second indicator and/or thethird indicator may be included in a sequence parameter set (SPS), apicture parameter set (PPS), a slice header, or a tile group header in abitstream.

The above-mentioned problem is also solved by the disclosure in furtherproviding a motion vector compression method, comprising: obtaining atemporal motion vector; determining an exponent part or a mantissa partof the temporal motion vector; performing at least one bit shiftoperation based on the exponent part or the mantissa part of thetemporal motion vector to obtain a compressed motion vector, wherein theexponent part corresponds to Least Significant Bit (LSB) of thecompressed motion vector and the mantissa part corresponds to MostSignificant Bit (MSB) of the compressed motion vector; performing atemporal motion vector prediction (TMVP) using the compressed motionvector.

The above-mentioned problem is further solved by the disclosure inproviding a coding method based on a motion vector, comprising: coding afirst flag; performing a first method, when the first flag is a firstvalue; and performing a second method, when the first flag is a secondvalue, wherein the first value is different from the second value,wherein an original value of a first motion vector component of acurrent image block is binarized by M bits, wherein the first methodcomprises: applying a right shift of N bit to the original value,wherein (M-N) equals to a predetermined value, and wherein N and M arepositive integers; setting the right shifted original value as a storagevalue of the first motion vector component; and coding a subsequentimage block based on the storage value; and wherein the second methodcomprises: applying a clipping operation to the original value, whereina clipped motion vector component represented by the clipped originalvalue is restricted between −2^(M-N-1) and 2^(M-N-1)−1; setting theclipped original value as the storage value of the first motion vectorcomponent; and coding a subsequent image block based on the storagevalue.

In an embodiment, after setting the right shifted original value as thestorage value of the motion vector according to the first method, themethod may further comprise: applying a left shift of N bit to thestorage value; wherein coding the subsequent image block based on thestorage value comprises: coding the subsequent image block based on theleft shifted storage value.

Alternatively, after setting the clipped original value as the storagevalue of the motion vector according to the second method, the methodmay further comprise: determining a restoration value of the firstmotion vector component based on the storage value, wherein therestoration value is binarized by M bits, wherein the last (M−N) bits ofthe restoration value is the same as the storage value, and wherein eachof the first N bits of the restoration value equals to 0, when thestorage value is positive, and each of the first N bits of therestoration value equals to 1, when the storage value is negative;wherein coding the subsequent image block based on the storage valuecomprises: coding the subsequent image block based on the restorationvalue.

In an embodiment, the subsequent image block and the current block maybe in different pictures, and the prediction mode of the subsequentimage block may comprise temporal motion vector prediction (TMVP) and/oralternative temporal motion vector prediction (ATMVP).

In another embodiment, the first flag may be coded for each picture; or,the first flag may be coded for each tile; or, the first flag may becoded for each tile set; or, the first flag may be coded for each slice.

In still another embodiment, the first flag may be included in asequence parameter set (SPS), a picture parameter set (PPS), a sliceheader, or a tile group header in a bitstream.

According to an embodiment, the current image block may further have asecond motion vector component, and the coding method may furthercomprise: coding a second flag; wherein: the first method may beperformed for the second motion vector component, when the second flagis the first value; and the second method may be performed for thesecond motion vector component, when the second flag is the secondvalue.

According to another embodiment, before coding the first flag, thecoding method may further comprise: determining if a resolution of acurrent picture is larger than or equal to a first preset value, and thecurrent image block may be in the current picture.

Further, when the resolution of the current picture is smaller than thefirst preset value, the second method may be performed.

Moreover, when the current picture is divided into tile sets, the secondmethod may be performed; or when a resolution of a tile set is smallerthan a second preset value, the second method may be performed.

According to an embodiment, before coding the first flag, the codingmethod may further comprise: determining if a size of a coding tree unit(CTU), a coding unit (CU), an image block, or a unit of a current imageblock satisfies a first size condition.

Further, if the size of CTU, CU, image block or unit of the currentimage block satisfies a second size condition, the first method may beperformed; or, if the size of CTU, CU, image block, or unit of thecurrent image block satisfies a third size condition, the second methodmay be performed.

The disclosure also provides a coding method based on a motion vector,comprising: determining a size of a CTU, a CU, an image block, or a unitof a current image block; and performing at least one of a first methodand a second method based on the size, or determining a resolution of acurrent picture; and performing at least one of the first method and thesecond method based on the resolution, wherein an original value of afirst motion vector component of the current image block is binarized byM bits, wherein the first method comprises: applying a right shift of Nbit to the original value, wherein (M-N) equals to a predeterminedvalue, and wherein N and M are positive integers; setting the rightshifted original value as a storage value of the first motion vectorcomponent; and coding a subsequent image block based on the storagevalue; and wherein the second method comprises: applying a clippingoperation to the original value, wherein a clipped motion vectorcomponent represented by the clipped original value is restrictedbetween −2^(M-N-1) and 2^(M-N-1)−1; setting the clipped original valueas the storage value of the first motion vector component; and coding asubsequent image block based on the storage value.

The above-mentioned problem is also solved by anon-transitorycomputer-readable storage medium storing programming for execution by aprocessing circuitry, wherein the programming, when executed by theprocessing circuitry, configures the processing circuitry to carry outany one of the methods described above.

The above-mentioned problem is also solved by a decoder, comprisingcircuitry configured to perform any one of the methods described above.

The above-mentioned problem is also solved by an encoder, comprisingcircuitry configured to perform any one of the methods described above.

The coding described above can be an encoding or a decoding.

Additional features and advantages of the present disclosure will bedescribed with reference to the drawings. In the description, referenceis made to the accompanying figures that are meant to illustratepreferred embodiments of the disclosure. It is understood that suchembodiments do not represent the full scope of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following embodiments of the application are described in moredetail with reference to the attached figures and drawings, in which:

FIG. 1A is a block diagram showing an example of a video coding systemconfigured to implement embodiments of the application;

FIG. 1B is a block diagram showing another example of a video codingsystem configured to implement embodiments of the application;

FIG. 2 is a block diagram showing an example of a video encoderconfigured to implement embodiments of the application;

FIG. 3 is a block diagram showing an example structure of a videodecoder configured to implement embodiments of the application;

FIG. 4 is a block diagram illustrating an example of an encodingapparatus or a decoding apparatus;

FIG. 5 is a block diagram illustrating another example of an encodingapparatus or a decoding apparatus;

FIG. 6 is a diagram showing an example of an implement embodiment of theapplication;

FIG. 7 is a diagram showing an example of another implement embodimentof the application;

FIG. 8 is a diagram showing an example of another implement embodimentof the application;

FIG. 9 is a diagram showing an example of another implement embodimentof the application; and

FIG. 10 is a flow diagram showing a motion vector compression methodaccording to the disclosure.

In the following, identical reference signs refer to identical or atleast functionally equivalent features if not explicitly specifiedotherwise.

DETAILED DESCRIPTION OF THE EMBODIMENTS

In the following description, reference is made to the accompanyingfigures, which form part of the disclosure, and which show, by way ofillustration, specific aspects of embodiments of the application orspecific aspects in which embodiments of the present application may beused. It is understood that embodiments of the application may be usedin other aspects and comprise structural or logical changes not depictedin the figures. The following detailed description, therefore, is not tobe taken in a limiting sense, and the scope of the present applicationis defined by the appended claims.

For instance, it is understood that a disclosure in connection with adescribed method may also hold true for a corresponding device or systemconfigured to perform the method and vice versa. For example, if one ora plurality of specific method operations are described, a correspondingdevice may include one or a plurality of units, e.g. functional units,to perform the described one or plurality of method operations (e.g. oneunit performing the one or plurality of operations, or a plurality ofunits each performing one or more of the plurality of operations), evenif such one or more units are not explicitly described or illustrated inthe figures. On the other hand, for example, if a specific apparatus isdescribed based on one or a plurality of units, e.g. functional units, acorresponding method may include one operation to perform thefunctionality of the one or plurality of units (e.g. one operationperforming the functionality of the one or plurality of units, or aplurality of operations each performing the functionality of one or moreof the plurality of units), even if such one or plurality of operationsare not explicitly described or illustrated in the figures. Further, itis understood that the features of the various exemplary embodimentsand/or aspects described herein may be combined with each other, unlessspecifically noted otherwise.

Video coding typically refers to the processing of a sequence ofpictures, which form the video or video sequence. Instead of the term“picture” the term “frame” or “image” may be used as synonyms in thefield of video coding. Video coding (or coding in general) comprises twoparts video encoding and video decoding. Video encoding is performed atthe source side, typically comprising processing (e.g. by compression)the original video pictures to reduce the amount of data required forrepresenting the video pictures (for more efficient storage and/ortransmission). Video decoding is performed at the destination side andtypically comprises the inverse processing compared to the encoder toreconstruct the video pictures. Embodiments referring to “coding” ofvideo pictures (or pictures in general) shall be understood to relate to“encoding” or “decoding” of video pictures or respective videosequences. The combination of the encoding part and the decoding part isalso referred to as CODEC (Coding and Decoding).

In case of lossless video coding, the original video pictures can bereconstructed, i.e. the reconstructed video pictures have the samequality as the original video pictures (assuming no transmission loss orother data loss during storage or transmission). In case of lossy videocoding, further compression, e.g. by quantization, is performed, toreduce the amount of data representing the video pictures, which cannotbe completely reconstructed at the decoder, i.e. the quality of thereconstructed video pictures is lower or worse compared to the qualityof the original video pictures.

Several video coding standards belong to the group of “lossy hybridvideo codecs” (i.e. combine spatial and temporal prediction in thesample domain and 2D transform coding for applying quantization in thetransform domain). Each picture of a video sequence is typicallypartitioned into a set of non-overlapping blocks and the coding istypically performed on a block level. In other words, at the encoder thevideo is typically processed, i.e. encoded, on a block (video block)level, e.g. by using spatial (intra picture) prediction and/or temporal(inter picture) prediction to generate a prediction block, subtractingthe prediction block from the current block (block currentlyprocessed/to be processed) to obtain a residual block, transforming theresidual block and quantizing the residual block in the transform domainto reduce the amount of data to be transmitted (compression), whereas atthe decoder the inverse processing compared to the encoder is applied tothe encoded or compressed block to reconstruct the current block forrepresentation. Furthermore, the encoder duplicates the decoderprocessing loop such that both will generate identical predictions (e.g.intra- and inter predictions) and/or re-constructions for processing,i.e. coding, the subsequent blocks.

In the following embodiments of a video coding system 10, a videoencoder 20 and a video decoder 30 are described based on FIGS. 1 to 3 .

FIG. 1A is a schematic block diagram illustrating an example codingsystem 10, e.g. a video coding system 10 (or short coding system 10)that may utilize techniques of this present application. Video encoder20 (or short encoder 20) and video decoder 30 (or short decoder 30) ofvideo coding system 10 represent examples of devices that may beconfigured to perform techniques in accordance with various examplesdescribed in the present application.

As shown in FIG. 1A, the coding system 10 comprises a source device 12configured to provide encoded picture data 21 e.g. to a destinationdevice 14 for decoding the encoded picture data 13.

The source device 12 comprises an encoder 20, and may additionally, i.e.optionally, comprise a picture source 16, a pre-processor (orpre-processing unit) 18, e.g. a picture pre-processor 18, and acommunication interface or communication unit 22.

The picture source 16 may comprise or be any kind of picture capturingdevice, for example a camera for capturing a real-world picture, and/orany kind of a picture generating device, for example a computer-graphicsprocessor for generating a computer animated picture, or any kind ofother device for obtaining and/or providing a real-world picture, acomputer generated picture (e.g. a screen content, a virtual reality(VR) picture) and/or any combination thereof (e.g. an augmented reality(AR) picture). The picture source may be any kind of memory or storagestoring any of the aforementioned pictures.

In distinction to the pre-processor 18 and the processing performed bythe pre-processing unit 18, the picture or picture data 17 may also bereferred to as raw picture or raw picture data 17.

Pre-processor 18 is configured to receive the (raw) picture data 17 andto perform pre-processing on the picture data 17 to obtain apre-processed picture 19 or pre-processed picture data 19.Pre-processing performed by the pre-processor 18 may, e.g., comprisetrimming, color format conversion (e.g. from RGB to YCbCr), colorcorrection, or de-noising. It can be understood that the pre-processingunit 18 may be optional component.

The video encoder 20 is configured to receive the pre-processed picturedata 19 and provide encoded picture data 21 (further details will bedescribed below, e.g., based on FIG. 2 ).

Communication interface 22 of the source device 12 may be configured toreceive the encoded picture data 21 and to transmit the encoded picturedata 21 (or any further processed version thereof) over communicationchannel 13 to another device, e.g. the destination device 14 or anyother device, for storage or direct reconstruction.

The destination device 14 comprises a decoder 30 (e.g. a video decoder30), and may additionally, i.e. optionally, comprise a communicationinterface or communication unit 28, a post-processor 32 (orpost-processing unit 32) and a display device 34.

The communication interface 28 of the destination device 14 isconfigured receive the encoded picture data 21 (or any further processedversion thereof), e.g. directly from the source device 12 or from anyother source, e.g. a storage device, e.g. an encoded picture datastorage device, and provide the encoded picture data 21 to the decoder30.

The communication interface 22 and the communication interface 28 may beconfigured to transmit or receive the encoded picture data 21 or encodeddata 13 via a direct communication link between the source device 12 andthe destination device 14, e.g. a direct wired or wireless connection,or via any kind of network, e.g. a wired or wireless network or anycombination thereof, or any kind of private and public network, or anykind of combination thereof.

The communication interface 22 may be, e.g., configured to package theencoded picture data 21 into an appropriate format, e.g. packets, and/orprocess the encoded picture data using any kind of transmission encodingor processing for transmission over a communication link orcommunication network.

The communication interface 28, forming the counterpart of thecommunication interface 22, may be, e.g., configured to receive thetransmitted data and process the transmission data using any kind ofcorresponding transmission decoding or processing and/or de-packaging toobtain the encoded picture data 21.

Both, communication interface 22 and communication interface 28 may beconfigured as unidirectional communication interfaces as indicated bythe arrow for the communication channel 13 in FIG. 1A pointing from thesource device 12 to the destination device 14, or bi-directionalcommunication interfaces, and may be configured, e.g. to send andreceive messages, e.g. to set up a connection, to acknowledge andexchange any other information related to the communication link and/ordata transmission, e.g. encoded picture data transmission.

The decoder 30 is configured to receive the encoded picture data 21 andprovide decoded picture data 31 or a decoded picture 31 (further detailswill be described below, e.g., based on FIG. 3 or FIG. 5 ).

The post-processor 32 of destination device 14 is configured topost-process the decoded picture data 31 (also called reconstructedpicture data), e.g. the decoded picture 31, to obtain post-processedpicture data 33, e.g. a post-processed picture 33. The post-processingperformed by the post-processing unit 32 may comprise, e.g. color formatconversion (e.g. from YCbCr to RGB), color correction, trimming, orre-sampling, or any other processing, e.g. for preparing the decodedpicture data 31 for display, e.g. by display device 34.

The display device 34 of the destination device 14 is configured toreceive the post-processed picture data 33 for displaying the picture,e.g. to a user or viewer. The display device 34 may be or comprise anykind of display for representing the reconstructed picture, e.g. anintegrated or external display or monitor. The displays may, e.g.comprise liquid crystal displays (LCD), organic light emitting diodes(OLED) displays, plasma displays, projectors, micro LED displays, liquidcrystal on silicon (LCoS), digital light processor (DLP) or any kind ofother display.

Although FIG. 1A depicts the source device 12 and the destination device14 as separate devices, embodiments of devices may also comprise both orboth functionalities, the source device 12 or correspondingfunctionality and the destination device 14 or correspondingfunctionality. In such embodiments the source device 12 or correspondingfunctionality and the destination device 14 or correspondingfunctionality may be implemented using the same hardware and/or softwareor by separate hardware and/or software or any combination thereof.

As will be apparent for the skilled person based on the description, theexistence and (exact) split of functionalities of the different units orfunctionalities within the source device 12 and/or destination device 14as shown in FIG. 1A may vary depending on the actual device andapplication.

The encoder 20 (e.g. a video encoder 20) or the decoder 30 (e.g. a videodecoder 30) or both encoder 20 and decoder 30 may be implemented viaprocessing circuitry as shown in FIG. 1B, such as one or moremicroprocessors, digital signal processors (DSPs), application-specificintegrated circuits (ASICs), field-programmable gate arrays (FPGAs),discrete logic, hardware, video coding dedicated or any combinationsthereof. The encoder 20 may be implemented via processing circuitry 46to embody the various modules as discussed with respect to encoder 20 ofFIG. 2 and/or any other encoder system or subsystem described herein.The decoder 30 may be implemented via processing circuitry 46 to embodythe various modules as discussed with respect to decoder 30 of FIG. 3and/or any other decoder system or subsystem described herein. Theprocessing circuitry may be configured to perform the various operationsas discussed later. As shown in FIG. 5 , if the techniques areimplemented partially in software, a device may store instructions forthe software in a suitable, non-transitory computer-readable storagemedium and may execute the instructions in hardware using one or moreprocessors to perform the techniques of this disclosure. Either of videoencoder 20 and video decoder 30 may be integrated as part of a combinedencoder/decoder (CODEC) in a single device, for example, as shown inFIG. 1B.

Source device 12 and destination device 14 may comprise any of a widerange of devices, including any kind of handheld or stationary devices,e.g. notebook or laptop computers, mobile phones, smart phones, tabletsor tablet computers, cameras, desktop computers, set-top boxes,televisions, display devices, digital media players, video gamingconsoles, video streaming devices (such as content services servers orcontent delivery servers), broadcast receiver device, broadcasttransmitter device, or the like and may use no or any kind of operatingsystem. In some cases, the source device 12 and the destination device14 may be equipped for wireless communication. Thus, the source device12 and the destination device 14 may be wireless communication devices.

In some cases, video coding system 10 illustrated in FIG. 1A is merelyan example and the techniques of the present application may apply tovideo coding settings (e.g., video encoding or video decoding) that donot necessarily include any data communication between the encoding anddecoding devices. In other examples, data is retrieved from a localmemory, streamed over a network, or the like. A video encoding devicemay encode and store data to memory, and/or a video decoding device mayretrieve and decode data from memory. In some examples, the encoding anddecoding is performed by devices that do not communicate with oneanother, but simply encode data to memory and/or retrieve and decodedata from memory.

For convenience of description, embodiments of the application aredescribed herein, for example, by reference to High-Efficiency VideoCoding (HEVC) or to the reference software of Versatile Video coding(VVC), the next generation video coding standard developed by the JointCollaboration Team on Video Coding (JCT-VC) of ITU-T Video CodingExperts Group (VCEG) and ISO/IEC Motion Picture Experts Group (MPEG).One of ordinary skill in the art will understand that embodiments of theapplication are not limited to HEVC or VVC.

Encoder and Encoding Method

FIG. 2 shows a schematic block diagram of an example video encoder 20that is configured to implement the techniques of the presentapplication. In the example of FIG. 2 , the video encoder 20 comprisesan input 201 (or input interface 201), a residual calculation unit 204,a transform processing unit 206, a quantization unit 208, an inversequantization unit 210, and inverse transform processing unit 212, areconstruction unit 214, a loop filter unit 220, a decoded picturebuffer (DPB) 230, a mode selection unit 260, an entropy encoding unit270 and an output 272 (or output interface 272). The mode selection unit260 may include an inter prediction unit 244, an intra prediction unit254 and a partitioning unit 262. Inter prediction unit 244 may include amotion estimation unit and a motion compensation unit (not shown). Avideo encoder 20 as shown in FIG. 2 may also be referred to as hybridvideo encoder or a video encoder according to a hybrid video codec.

The residual calculation unit 204, the transform processing unit 206,the quantization unit 208, the mode selection unit 260 may be referredto as forming a forward signal path of the encoder 20, whereas theinverse quantization unit 210, the inverse transform processing unit212, the reconstruction unit 214, the buffer 216, the loop filter 220,the decoded picture buffer (DPB) 230, the inter prediction unit 244 andthe intra-prediction unit 254 may be referred to as forming a backwardsignal path of the video encoder 20, wherein the backward signal path ofthe video encoder 20 corresponds to the signal path of the decoder (seevideo decoder 30 in FIG. 3 ). The inverse quantization unit 210, theinverse transform processing unit 212, the reconstruction unit 214, theloop filter 220, the decoded picture buffer (DPB) 230, the interprediction unit 244 and the intra-prediction unit 254 are also referredto forming the “built-in decoder” of video encoder 20.

Pictures & Picture Partitioning (Pictures & Blocks)

The encoder 20 may be configured to receive, e.g. via input 201, apicture 17 (or picture data 17), e.g. picture of a sequence of picturesforming a video or video sequence. The received picture or picture datamay also be a pre-processed picture 19 (or pre-processed picture data19). For sake of simplicity the following description refers to thepicture 17. The picture 17 may also be referred to as current picture orpicture to be coded (in particular in video coding to distinguish thecurrent picture from other pictures, e.g. previously encoded and/ordecoded pictures of the same video sequence, i.e. the video sequencewhich also comprises the current picture).

A (digital) picture is or can be regarded as a two-dimensional array ormatrix of samples with intensity values. A sample in the array may alsobe referred to as pixel (short form of picture element) or a pel. Thenumber of samples in horizontal and vertical direction (or axis) of thearray or picture define the size and/or resolution of the picture. Forrepresentation of color, typically three color components are employed,i.e. the picture may be represented or include three sample arrays. InRBG format or color space a picture comprises a corresponding red, greenand blue sample array. However, in video coding each pixel is typicallyrepresented in a luminance and chrominance format or color space, e.g.YCbCr, which comprises a luminance component indicated by Y (sometimesalso L is used instead) and two chrominance components indicated by Cband Cr. The luminance (or short luma) component Y represents thebrightness or grey level intensity (e.g. like in a grey-scale picture),while the two chrominance (or short chroma) components Cb and Crrepresent the chromaticity or color information components. Accordingly,a picture in YCbCr format comprises a luminance sample array ofluminance sample values (Y), and two chrominance sample arrays ofchrominance values (Cb and Cr). Pictures in RGB format may be convertedor transformed into YCbCr format and vice versa, the process is alsoknown as color transformation or conversion. If a picture is monochrome,the picture may comprise only a luminance sample array. Accordingly, apicture may be, for example, an array of luma samples in monochromeformat or an array of luma samples and two corresponding arrays ofchroma samples in 4:2:0, 4:2:2, and 4:4:4 colour format.

Embodiments of the video encoder 20 may comprise a picture partitioningunit (not depicted in FIG. 2 ) configured to partition the picture 17into a plurality of (typically non-overlapping) picture blocks 203.These blocks may also be referred to as root blocks, macro blocks(H.264/AVC) or coding tree blocks (CTB) or coding tree units (CTU)(H.265/HEVC and VVC). The picture partitioning unit may be configured touse the same block size for all pictures of a video sequence and thecorresponding grid defining the block size, or to change the block sizebetween pictures or subsets or groups of pictures, and partition eachpicture into the corresponding blocks.

In further embodiments, the video encoder may be configured to receivedirectly a block 203 of the picture 17, e.g. one, several or all blocksforming the picture 17. The picture block 203 may also be referred to ascurrent picture block or picture block to be coded.

Like the picture 17, the picture block 203 again is or can be regardedas a two-dimensional array or matrix of samples with intensity values(sample values), although of smaller dimension than the picture 17. Inother words, the block 203 may comprise, e.g., one sample array (e.g. aluma array in case of a monochrome picture 17, or a luma or chroma arrayin case of a color picture) or three sample arrays (e.g. a luma and twochroma arrays in case of a color picture 17) or any other number and/orkind of arrays depending on the color format applied. The number ofsamples in horizontal and vertical direction (or axis) of the block 203define the size of block 203. Accordingly, a block may, for example, anM×N (M-column by N-row) array of samples, or an M×N array of transformcoefficients.

Embodiments of the video encoder 20 as shown in FIG. 2 may be configuredencode the picture 17 block by block, e.g. the encoding and predictionis performed per block 203.

Residual Calculation

The residual calculation unit 204 may be configured to calculate aresidual block 205 (also referred to as residual 205) based on thepicture block 203 and a prediction block 265 (further details about theprediction block 265 are provided later), e.g. by subtracting samplevalues of the prediction block 265 from sample values of the pictureblock 203, sample by sample (pixel by pixel) to obtain the residualblock 205 in the sample domain.

Transform

The transform processing unit 206 may be configured to apply atransform, e.g. a discrete cosine transform (DCT) or discrete sinetransform (DST), on the sample values of the residual block 205 toobtain transform coefficients 207 in a transform domain. The transformcoefficients 207 may also be referred to as transform residualcoefficients and represent the residual block 205 in the transformdomain.

The transform processing unit 206 may be configured to apply integerapproximations of DCT/DST, such as the transforms specified forH.265/HEVC. Compared to an orthogonal DCT transform, such integerapproximations are typically scaled by a certain factor. In order topreserve the norm of the residual block which is processed by forwardand inverse transforms, additional scaling factors are applied as partof the transform process. The scaling factors are typically chosen basedon certain constraints like scaling factors being a power of two forshift operations, bit depth of the transform coefficients, tradeoffbetween accuracy and implementation costs, etc. Specific scaling factorsare, for example, specified for the inverse transform, e.g. by inversetransform processing unit 212 (and the corresponding inverse transform,e.g. by inverse transform processing unit 312 at video decoder 30) andcorresponding scaling factors for the forward transform, e.g. bytransform processing unit 206, at an encoder 20 may be specifiedaccordingly.

Embodiments of the video encoder 20 (respectively transform processingunit 206) may be configured to output transform parameters, e.g. a typeof transform or transforms, e.g. directly or encoded or compressed viathe entropy encoding unit 270, so that, e.g., the video decoder 30 mayreceive and use the transform parameters for decoding.

Quantization

The quantization unit 208 may be configured to quantize the transformcoefficients 207 to obtain quantized coefficients 209, e.g. by applyingscalar quantization or vector quantization. The quantized coefficients209 may also be referred to as quantized transform coefficients 209 orquantized residual coefficients 209.

The quantization process may reduce the bit depth associated with someor all of the transform coefficients 207. For example, an n-bittransform coefficient may be rounded down to an m-bit Transformcoefficient during quantization, where n is greater than m. The degreeof quantization may be modified by adjusting a quantization parameter(QP). For example, for scalar quantization, different scaling may beapplied to achieve finer or coarser quantization. Smaller quantizationstep sizes correspond to finer quantization, whereas larger quantizationstep sizes correspond to coarser quantization. The applicablequantization step size may be indicated by a quantization parameter(QP). The quantization parameter may for example be an index to apredefined set of applicable quantization step sizes. For example, smallquantization parameters may correspond to fine quantization (smallquantization step sizes) and large quantization parameters maycorrespond to coarse quantization (large quantization step sizes) orvice versa. The quantization may include division by a quantization stepsize and a corresponding and/or the inverse dequantization, e.g. byinverse quantization unit 210, may include multiplication by thequantization step size. Embodiments according to some standards, e.g.HEVC, may be configured to use a quantization parameter to determine thequantization step size. Generally, the quantization step size may becalculated based on a quantization parameter using a fixed pointapproximation of an equation including division. Additional scalingfactors may be introduced for quantization and dequantization to restorethe norm of the residual block, which might get modified because of thescaling used in the fixed point approximation of the equation forquantization step size and quantization parameter. In one exampleimplementation, the scaling of the inverse transform and dequantizationmight be combined. Alternatively, customized quantization tables may beused and signaled from an encoder to a decoder, e.g. in a bitstream. Thequantization is a lossy operation, wherein the loss increases withincreasing quantization step sizes.

Embodiments of the video encoder 20 (respectively quantization unit 208)may be configured to output quantization parameters (QP), e.g. directlyor encoded via the entropy encoding unit 270, so that, e.g., the videodecoder 30 may receive and apply the quantization parameters fordecoding.

Inverse Quantization

The inverse quantization unit 210 is configured to apply the inversequantization of the quantization unit 208 on the quantized coefficientsto obtain dequantized coefficients 211, e.g. by applying the inverse ofthe quantization scheme applied by the quantization unit 208 based on orusing the same quantization step size as the quantization unit 208. Thedequantized coefficients 211 may also be referred to as dequantizedresidual coefficients 211 and correspond—although typically notidentical to the transform coefficients due to the loss byquantization—to the transform coefficients 207.

Inverse Transform

The inverse transform processing unit 212 is configured to apply theinverse transform of the transform applied by the transform processingunit 206, e.g. an inverse discrete cosine transform (DCT) or inversediscrete sine transform (DST) or other inverse transforms, to obtain areconstructed residual block 213 (or corresponding dequantizedcoefficients 213) in the sample domain. The reconstructed residual block213 may also be referred to as transform block 213.

Reconstruction

The reconstruction unit 214 (e.g. adder or summer 214) is configured toadd the transform block 213 (i.e. reconstructed residual block 213) tothe prediction block 265 to obtain a reconstructed block 215 in thesample domain, e.g. by adding—sample by sample—the sample values of thereconstructed residual block 213 and the sample values of the predictionblock 265.

Filtering

The loop filter unit 220 (or short “loop filter” 220), is configured tofilter the reconstructed block 215 to obtain a filtered block 221, or ingeneral, to filter reconstructed samples to obtain filtered samples. Theloop filter unit is, e.g., configured to smooth pixel transitions, orotherwise improve the video quality. The loop filter unit 220 maycomprise one or more loop filters such as a de-blocking filter, asample-adaptive offset (SAO) filter or one or more other filters, e.g. abilateral filter, an adaptive loop filter (ALF), a sharpening, asmoothing filters or a collaborative filters, or any combinationthereof. Although the loop filter unit 220 is shown in FIG. 2 as beingan in loop filter, in other configurations, the loop filter unit 220 maybe implemented as a post loop filter. The filtered block 221 may also bereferred to as filtered reconstructed block 221.

Embodiments of the video encoder 20 (respectively loop filter unit 220)may be configured to output loop filter parameters (such as sampleadaptive offset information), e.g. directly or encoded via the entropyencoding unit 270, so that, e.g., a decoder 30 may receive and apply thesame loop filter parameters or respective loop filters for decoding.

Decoded Picture Buffer

The decoded picture buffer (DPB) 230 may be a memory that storesreference pictures, or in general reference picture data, for encodingvideo data by video encoder 20. The DPB 230 may be formed by any of avariety of memory devices, such as dynamic random access memory (DRAM),including synchronous DRAM (SDRAM), magnetoresistive RAM (MRAM),resistive RAM (RRAM), or other types of memory devices. The decodedpicture buffer (DPB) 230 may be configured to store one or more filteredblocks 221. The decoded picture buffer 230 may be further configured tostore other previously filtered blocks, e.g. previously reconstructedand filtered blocks 221, of the same current picture or of differentpictures, e.g. previously reconstructed pictures, and may providecomplete previously reconstructed, i.e. decoded, pictures (andcorresponding reference blocks and samples) and/or a partiallyreconstructed current picture (and corresponding reference blocks andsamples), for example for inter prediction. The decoded picture buffer(DPB) 230 may be also configured to store one or more unfilteredreconstructed blocks 215, or in general unfiltered reconstructedsamples, e.g. if the reconstructed block 215 is not filtered by loopfilter unit 220, or any other further processed version of thereconstructed blocks or samples.

Mode Selection (Partitioning & Prediction)

The mode selection unit 260 comprises partitioning unit 262,inter-prediction unit 244 and intra-prediction unit 254, and isconfigured to receive or obtain original picture data, e.g. an originalblock 203 (current block 203 of the current picture 17), andreconstructed picture data, e.g. filtered and/or unfilteredreconstructed samples or blocks of the same (current) picture and/orfrom one or a plurality of previously decoded pictures, e.g. fromdecoded picture buffer 230 or other buffers (e.g. line buffer, notshown). The reconstructed picture data is used as reference picture datafor prediction, e.g. inter-prediction or intra-prediction, to obtain aprediction block 265 or predictor 265.

Mode selection unit 260 may be configured to determine or select apartitioning for a current block prediction mode (including nopartitioning) and a prediction mode (e.g. an intra or inter predictionmode) and generate a corresponding prediction block 265, which is usedfor the calculation of the residual block 205 and for the reconstructionof the reconstructed block 215.

Embodiments of the mode selection unit 260 may be configured to selectthe partitioning and the prediction mode (e.g. from those supported byor available for mode selection unit 260), which provide the best matchor in other words the minimum residual (minimum residual means bettercompression for transmission or storage), or a minimum signalingoverhead (minimum signaling overhead means better compression fortransmission or storage), or which considers or balances both. The modeselection unit 260 may be configured to determine the partitioning andprediction mode based on rate distortion optimization (RDO), i.e. selectthe prediction mode which provides a minimum rate distortion. Terms like“best”, “minimum”, “optimum” etc. in this context do not necessarilyrefer to an overall “best”, “minimum”, “optimum”, etc. but may alsorefer to the fulfillment of a termination or selection criterion like avalue exceeding or falling below a threshold or other constraintsleading potentially to a “sub-optimum selection” but reducing complexityand processing time.

In other words, the partitioning unit 262 may be configured to partitionthe block 203 into smaller block partitions or sub-blocks (which formagain blocks), e.g. iteratively using quad-tree-partitioning (QT),binary partitioning (BT) or triple-tree-partitioning (TT) or anycombination thereof, and to perform, e.g., the prediction for each ofthe block partitions or sub-blocks, wherein the mode selection comprisesthe selection of the tree-structure of the partitioned block 203 and theprediction modes are applied to each of the block partitions orsub-blocks.

In the following the partitioning (e.g. by partitioning unit 260) andprediction processing (by inter-prediction unit 244 and intra-predictionunit 254) performed by an example video encoder 20 will be explained inmore detail.

Partitioning

The partitioning unit 262 may partition (or split) a current block 203into smaller partitions, e.g. smaller blocks of square or rectangularsize. These smaller blocks (which may also be referred to as sub-blocks)may be further partitioned into even smaller partitions. This is alsoreferred to tree-partitioning or hierarchical tree-partitioning, whereina root block, e.g. at root tree-level 0 (hierarchy-level 0, depth 0),may be recursively partitioned, e.g. partitioned into two or more blocksof a next lower tree-level, e.g. nodes at tree-level 1 (hierarchy-level1, depth 1), wherein these blocks may be again partitioned into two ormore blocks of a next lower level, e.g. tree-level 2 (hierarchy-level 2,depth 2), etc. until the partitioning is terminated, e.g. because atermination criterion is fulfilled, e.g. a maximum tree depth or minimumblock size is reached. Blocks which are not further partitioned are alsoreferred to as leaf-blocks or leaf nodes of the tree. A tree usingpartitioning into two partitions is referred to as binary-tree (BT), atree using partitioning into three partitions is referred to asternary-tree (TT), and a tree using partitioning into four partitions isreferred to as quad-tree (QT).

As mentioned before, the term “block” as used herein may be a portion,in particular a square or rectangular portion, of a picture. Withreference, for example, to HEVC and VVC, the block may be or correspondto a coding tree unit (CTU), a coding unit (CU), prediction unit (PU),and transform unit (TU) and/or to the corresponding blocks, e.g. acoding tree block (CTB), a coding block (CB), a transform block (TB) orprediction block (PB).

For example, a coding tree unit (CTU) may be or comprise a CTB of lumasamples, two corresponding CTBs of chroma samples of a picture that hasthree sample arrays, or a CTB of samples of a monochrome picture or apicture that is coded using three separate colour planes and syntaxstructures used to code the samples. Correspondingly, a coding treeblock (CTB) may be an N×N block of samples for some value of N such thatthe division of a component into CTBs is a partitioning. A coding unit(CU) may be or comprise a coding block of luma samples, twocorresponding coding blocks of chroma samples of a picture that hasthree sample arrays, or a coding block of samples of a monochromepicture or a picture that is coded using three separate colour planesand syntax structures used to code the samples. Correspondingly a codingblock (CB) may be an M×N block of samples for some values of M and Nsuch that the division of a CTB into coding blocks is a partitioning.

In embodiments, e.g., according to HEVC, a coding tree unit (CTU) may besplit into CUs by using a quad-tree structure denoted as coding tree.The decision whether to code a picture area using inter-picture(temporal) or intra-picture (spatial) prediction is made at the CUlevel. Each CU can be further split into one, two or four PUs accordingto the PU splitting type. Inside one PU, the same prediction process isapplied and the relevant information is transmitted to the decoder on aPU basis. After obtaining the residual block by applying the predictionprocess based on the PU splitting type, a CU can be partitioned intotransform units (TUs) according to another quadtree structure similar tothe coding tree for the CU.

In embodiments, e.g., according to the latest video coding standardcurrently in development, which is referred to as Versatile Video Coding(VVC), Quad-tree and binary tree (QTBT) partitioning is used topartition a coding block. In the QTBT block structure, a CU can haveeither a square or rectangular shape. For example, a coding tree unit(CTU) is first partitioned by a quadtree structure. The quadtree leafnodes are further partitioned by a binary tree or ternary (or triple)tree structure. The partitioning tree leaf nodes are called coding units(CUs), and that segmentation is used for prediction and transformprocessing without any further partitioning. This means that the CU, PUand TU have the same block size in the QTBT coding block structure. Inparallel, multiple partition, for example, triple tree partition wasalso proposed to be used together with the QTBT block structure.

In one example, the mode selection unit 260 of video encoder 20 may beconfigured to perform any combination of the partitioning techniquesdescribed herein.

As described above, the video encoder 20 is configured to determine orselect the best or an optimum prediction mode from a set of(pre-determined) prediction modes. The set of prediction modes maycomprise, e.g., intra-prediction modes and/or inter-prediction modes.

Intra-Prediction

The set of intra-prediction modes may comprise 35 differentintra-prediction modes, e.g. non-directional modes like DC (or mean)mode and planar mode, or directional modes, e.g. as defined in HEVC, ormay comprise 67 different intra-prediction modes, e.g. non-directionalmodes like DC (or mean) mode and planar mode, or directional modes, e.g.as defined for VVC.

The intra-prediction unit 254 is configured to use reconstructed samplesof neighboring blocks of the same current picture to generate anintra-prediction block 265 according to an intra-prediction mode of theset of intra-prediction modes.

The intra prediction unit 254 (or in general the mode selection unit260) is further configured to output intra-prediction parameters (or ingeneral information indicative of the selected intra prediction mode forthe block) to the entropy encoding unit 270 in form of syntax elements266 for inclusion into the encoded picture data 21, so that, e.g., thevideo decoder 30 may receive and use the prediction parameters fordecoding.

Inter-Prediction

The set of (or possible) inter-prediction modes depends on the availablereference pictures (i.e. previous at least partially decoded pictures,e.g. stored in DBP 230) and other inter-prediction parameters, e.g.whether the whole reference picture or only a part, e.g. a search windowarea around the area of the current block, of the reference picture isused for searching for a best matching reference block, and/or e.g.whether pixel interpolation is applied, e.g. half/semi-pel and/orquarter-pel interpolation, or not.

Additional to the above prediction modes, skip mode and/or direct modemay be applied.

The inter prediction unit 244 may include a motion estimation (ME) unitand a motion compensation (MC) unit (both not shown in FIG. 2 ). Themotion estimation unit may be configured to receive or obtain thepicture block 203 (current picture block 203 of the current picture 17)and a decoded picture 231, or at least one or a plurality of previouslyreconstructed blocks, e.g. reconstructed blocks of one or a plurality ofother/different previously decoded pictures 231, for motion estimation.E.g. a video sequence may comprise the current picture and thepreviously decoded pictures 231, or in other words, the current pictureand the previously decoded pictures 231 may be part of or form asequence of pictures forming a video sequence.

The encoder 20 may, e.g., be configured to select a reference block froma plurality of reference blocks of the same or different pictures of theplurality of other pictures and provide a reference picture (orreference picture index) and/or an offset (spatial offset) between theposition (x, y coordinates) of the reference block and the position ofthe current block as inter prediction parameters to the motionestimation unit. This offset is also called motion vector (MV).

The motion compensation unit is configured to obtain, e.g. receive, aninter prediction parameter and to perform inter prediction based on orusing the inter prediction parameter to obtain an inter prediction block265. Motion compensation, performed by the motion compensation unit, mayinvolve fetching or generating the prediction block based on themotion/block vector determined by motion estimation, possibly performinginterpolations to sub-pixel precision. Interpolation filtering maygenerate additional pixel samples from known pixel samples, thuspotentially increasing the number of candidate prediction blocks thatmay be used to code a picture block. Upon receiving the motion vectorfor the PU of the current picture block, the motion compensation unitmay locate the prediction block to which the motion vector points in oneof the reference picture lists.

Motion compensation unit may also generate syntax elements associatedwith the blocks and the video slice for use by video decoder 30 indecoding the picture blocks of the video slice.

Entropy Coding

The entropy encoding unit 270 is configured to apply, for example, anentropy encoding algorithm or scheme (e.g. a variable length coding(VLC) scheme, an context adaptive VLC scheme (CAVLC), an arithmeticcoding scheme, a binarization, a context adaptive binary arithmeticcoding (CABAC), syntax-based context-adaptive binary arithmetic coding(SBAC), probability interval partitioning entropy (PIPE) coding oranother entropy encoding methodology or technique) or bypass (nocompression) on the quantized coefficients 209, inter predictionparameters, intra prediction parameters, loop filter parameters and/orother syntax elements to obtain encoded picture data 21 which can beoutput via the output 272, e.g. in the form of an encoded bitstream 21,so that, e.g., the video decoder 30 may receive and use the parametersfor decoding. The encoded bitstream 21 may be transmitted to videodecoder 30, or stored in a memory for later transmission or retrieval byvideo decoder 30.

Other structural variations of the video encoder 20 can be used toencode the video stream. For example, a non-transform based encoder 20can quantize the residual signal directly without the transformprocessing unit 206 for certain blocks or frames. In anotherimplementation, an encoder 20 can have the quantization unit 208 and theinverse quantization unit 210 combined into a single unit.

Decoder and Decoding Method

FIG. 3 shows an example of a video decoder 30 that is configured toimplement the techniques of this present application. The video decoder30 is configured to receive encoded picture data 21 (e.g. encodedbitstream 21), e.g. encoded by encoder 20, to obtain a decoded picture331. The encoded picture data or bitstream comprises information fordecoding the encoded picture data, e.g. data that represents pictureblocks of an encoded video slice and associated syntax elements.

In the example of FIG. 3 , the decoder 30 comprises an entropy decodingunit 304, an inverse quantization unit 310, an inverse transformprocessing unit 312, a reconstruction unit 314 (e.g. a summer 314), aloop filter 320, a decoded picture buffer (DBP) 330, an inter predictionunit 344 and an intra prediction unit 354. Inter prediction unit 344 maybe or include a motion compensation unit. Video decoder 30 may, in someexamples, perform a decoding pass generally reciprocal to the encodingpass described with respect to video encoder 100 from FIG. 2 .

As explained with regard to the encoder 20, the inverse quantizationunit 210, the inverse transform processing unit 212, the reconstructionunit 214 the loop filter 220, the decoded picture buffer (DPB) 230, theinter prediction unit 344 and the intra prediction unit 354 are alsoreferred to as forming the “built-in decoder” of video encoder 20.Accordingly, the inverse quantization unit 310 may be identical infunction to the inverse quantization unit 110, the inverse transformprocessing unit 312 may be identical in function to the inversetransform processing unit 212, the reconstruction unit 314 may beidentical in function to reconstruction unit 214, the loop filter 320may be identical in function to the loop filter 220, and the decodedpicture buffer 330 may be identical in function to the decoded picturebuffer 230. Therefore, the explanations provided for the respectiveunits and functions of the video 20 encoder apply correspondingly to therespective units and functions of the video decoder 30.

Entropy Decoding

The entropy decoding unit 304 is configured to parse the bitstream 21(or in general encoded picture data 21) and perform, for example,entropy decoding to the encoded picture data 21 to obtain, e.g.,quantized coefficients 309 and/or decoded coding parameters (not shownin FIG. 3 ), e.g. any or all of inter prediction parameters (e.g.reference picture index and motion vector), intra prediction parameter(e.g. intra prediction mode or index), transform parameters,quantization parameters, loop filter parameters, and/or other syntaxelements. Entropy decoding unit 304 maybe configured to apply thedecoding algorithms or schemes corresponding to the encoding schemes asdescribed with regard to the entropy encoding unit 270 of the encoder20. Entropy decoding unit 304 may be further configured to provide interprediction parameters, intra prediction parameter and/or other syntaxelements to the mode selection unit 360 and other parameters to otherunits of the decoder 30. Video decoder 30 may receive the syntaxelements at the video slice level and/or the video block level.

Inverse Quantization

The inverse quantization unit 310 may be configured to receivequantization parameters (QP) (or in general information related to theinverse quantization) and quantized coefficients from the encodedpicture data 21 (e.g. by parsing and/or decoding, e.g. by entropydecoding unit 304) and to apply based on the quantization parameters aninverse quantization on the decoded quantized coefficients 309 to obtaindequantized coefficients 311, which may also be referred to as transformcoefficients 311. The inverse quantization process may include use of aquantization parameter determined by video encoder 20 for each videoblock in the video slice to determine a degree of quantization and,likewise, a degree of inverse quantization that should be applied.

Inverse Transform

Inverse transform processing unit 312 may be configured to receivedequantized coefficients 311, also referred to as transform coefficients311, and to apply a transform to the dequantized coefficients 311 inorder to obtain reconstructed residual blocks 213 in the sample domain.The reconstructed residual blocks 213 may also be referred to astransform blocks 313. The transform may be an inverse transform, e.g.,an inverse DCT, an inverse DST, an inverse integer transform, or aconceptually similar inverse transform process. The inverse transformprocessing unit 312 may be further configured to receive transformparameters or corresponding information from the encoded picture data 21(e.g. by parsing and/or decoding, e.g. by entropy decoding unit 304) todetermine the transform to be applied to the dequantized coefficients311.

Reconstruction

The reconstruction unit 314 (e.g. adder or summer 314) may be configuredto add the reconstructed residual block 313, to the prediction block 365to obtain a reconstructed block 315 in the sample domain, e.g. by addingthe sample values of the reconstructed residual block 313 and the samplevalues of the prediction block 365.

Filtering

The loop filter unit 320 (either in the coding loop or after the codingloop) is configured to filter the reconstructed block 315 to obtain afiltered block 321, e.g. to smooth pixel transitions, or otherwiseimprove the video quality. The loop filter unit 320 may comprise one ormore loop filters such as a de-blocking filter, a sample-adaptive offset(SAO) filter or one or more other filters, e.g. a bilateral filter, anadaptive loop filter (ALF), a sharpening, a smoothing filters or acollaborative filters, or any combination thereof. Although the loopfilter unit 320 is shown in FIG. 3 as being an in loop filter, in otherconfigurations, the loop filter unit 320 may be implemented as a postloop filter.

Decoded Picture Buffer

The decoded video blocks 321 of a picture are then stored in decodedpicture buffer 330, which stores the decoded pictures 331 as referencepictures for subsequent motion compensation for other pictures and/orfor output respectively display.

The decoder 30 is configured to output the decoded picture 311, e.g. viaoutput 312, for presentation or viewing to a user.

Prediction

The inter prediction unit 344 may be identical to the inter predictionunit 244 (in particular to the motion compensation unit) and the intraprediction unit 354 may be identical to the inter prediction unit 254 infunction, and performs split or partitioning decisions and predictionbased on the partitioning and/or prediction parameters or respectiveinformation received from the encoded picture data 21 (e.g. by parsingand/or decoding, e.g. by entropy decoding unit 304). Mode selection unit360 may be configured to perform the prediction (intra or interprediction) per block based on reconstructed pictures, blocks orrespective samples (filtered or unfiltered) to obtain the predictionblock 365.

When the video slice is coded as an intra coded (I) slice, intraprediction unit 354 of mode selection unit 360 is configured to generateprediction block 365 for a picture block of the current video slicebased on a signaled intra prediction mode and data from previouslydecoded blocks of the current picture. When the video picture is codedas an inter coded (i.e., B, or P) slice, inter prediction unit 344 (e.g.motion compensation unit) of mode selection unit 360 is configured toproduce prediction blocks 365 for a video block of the current videoslice based on the motion vectors and other syntax elements receivedfrom entropy decoding unit 304. For inter prediction, the predictionblocks may be produced from one of the reference pictures within one ofthe reference picture lists. Video decoder 30 may construct thereference frame lists, List 0 and List 1, using default constructiontechniques based on reference pictures stored in DPB 330.

Mode selection unit 360 is configured to determine the predictioninformation for a video block of the current video slice by parsing themotion vectors and other syntax elements, and uses the predictioninformation to produce the prediction blocks for the current video blockbeing decoded. For example, the mode selection unit 360 uses some of thereceived syntax elements to determine a prediction mode (e.g., intra orinter prediction) used to code the video blocks of the video slice, aninter prediction slice type (e.g., B slice, P slice, or GPB slice),construction information for one or more of the reference picture listsfor the slice, motion vectors for each inter encoded video block of theslice, inter prediction status for each inter coded video block of theslice, and other information to decode the video blocks in the currentvideo slice.

Other variations of the video decoder 30 can be used to decode theencoded picture data 21. For example, the decoder 30 can produce theoutput video stream without the loop filtering unit 320. For example, anon-transform based decoder 30 can inverse-quantize the residual signaldirectly without the inverse-transform processing unit 312 for certainblocks or frames. In another implementation, the video decoder 30 canhave the inverse-quantization unit 310 and the inverse-transformprocessing unit 312 combined into a single unit.

It should be understood that, in the encoder 20 and the decoder 30, aprocessing result of a current operation may be further processed andthen output to the next operation. For example, after interpolationfiltering, motion vector derivation or loop filtering, a furtheroperation, such as Clip or shift, may be performed on the processingresult of the interpolation filtering, motion vector derivation or loopfiltering.

It should be noted that further operations may be applied to the derivedmotion vectors of current block (including but not limit to controlpoint motion vectors of affine mode, sub-block motion vectors in affine,planar, ATMVP modes, temporal motion vectors, and so on). For example,the value of motion vector is constrained to a predefined rangeaccording to its representing bit. If the representing bit of motionvector is bitDepth, then the range is −2{circumflex over( )}(bitDepth−1)˜2{circumflex over ( )}(bitDepth−1)−1, where“{circumflex over ( )}” means exponentiation. For example, if bitDepthis set equal to 16, the range is −32768˜32767; if bitDepth is set equalto 18, the range is −131072˜131071. Here provides two methods forconstraining the motion vector.

Method 1: remove the overflow MSB (most significant bit) by thefollowing operations:

ux=(mvx+2^(bitDepth))%2^(bitDepth)  (1)

mvx=(ux>=2^(bitDepth−1))?(ux−2^(bitDepth)):ux  (2)

uy=(mvy+2^(bitDepth))%2^(bitDepth)  (3)

mvy=(uy>=2^(bitDepth−1))?(uy−2^(bitDepth)):uy  (4)

For example, if the value of mvx is −32769, after applying formula (1)and (2), the resulting value is 32767. In computer system, decimalnumbers are stored as two's complement. The two's complement of −32769is 1,0111,1111,1111,1111 (17 bits), then the MSB is discarded, so theresulting two's complement is 0111,1111,1111,1111 (decimal number is32767), which is same as the output by applying formula (1) and (2).

ux=(mvpx+mvdx+2^(bitDepth))%2^(bitDepth)  (5)

mvx=(ux>=2^(bitDepth−1))?(ux−2^(bitDepth)):ux  (6)

uy=(mvpy+mvdy+2^(bitDepth))%2^(bitDepth)  (7)

mvy=(uy>=2^(bitDepth−1))?(uy−2^(bitDepth)):uy  (8)

The operations may be applied during the sum of mvp and mvd, as shown informula (5) to (8).

Method 2: remove the overflow MSB by clipping the value

vx=Clip3(−2^(bitDepth−1),2^(bitDepth−1)−1,vx)

vy=Clip3(−2^(bitDepth−1),2^(bitDepth−1)−1,vy)

where the definition of function Clip3 is as follow:

${{Clip}3\left( {x,y,z} \right)} = \left\{ \begin{matrix}{x\ } & ; & {z < x} \\{y\ } & ; & {z > y} \\{z\ } & ; & {otherwise}\end{matrix} \right.$

FIG. 4 is a schematic diagram of a video coding device 400 according toan embodiment of the disclosure. The video coding device 400 is suitablefor implementing the disclosed embodiments as described herein. In anembodiment, the video coding device 400 may be a decoder such as videodecoder 30 of FIG. 1A or an encoder such as video encoder 20 of FIG. 1A.

The video coding device 400 comprises ingress ports 410 (or input ports410) and receiver units (Rx) 420 for receiving data; a processor, logicunit, or central processing unit (CPU) 430 to process the data;transmitter units (Tx) 440 and egress ports 450 (or output ports 450)for transmitting the data; and a memory 460 for storing the data. Thevideo coding device 400 may also comprise optical-to-electrical (OE)components and electrical-to-optical (EO) components coupled to theingress ports 410, the receiver units 420, the transmitter units 440,and the egress ports 450 for egress or ingress of optical or electricalsignals.

The processor 430 is implemented by hardware and software. The processor430 may be implemented as one or more CPU chips, cores (e.g., as amulti-core processor), FPGAs, ASICs, and DSPs. The processor 430 is incommunication with the ingress ports 410, receiver units 420,transmitter units 440, egress ports 450, and memory 460. The processor430 comprises a coding module 470. The coding module 470 implements thedisclosed embodiments described above. For instance, the coding module470 implements, processes, prepares, or provides the various codingoperations. The inclusion of the coding module 470 therefore provides asubstantial improvement to the functionality of the video coding device400 and effects a transformation of the video coding device 400 to adifferent state. Alternatively, the coding module 470 is implemented asinstructions stored in the memory 460 and executed by the processor 430.

The memory 460 may comprise one or more disks, tape drives, andsolid-state drives and may be used as an over-flow data storage device,to store programs when such programs are selected for execution, and tostore instructions and data that are read during program execution.

The memory 460 may be, for example, volatile and/or non-volatile and maybe a read-only memory (ROM), random access memory (RAM), ternarycontent-addressable memory (TCAM), and/or static random-access memory(SRAM).

FIG. 5 is a simplified block diagram of an apparatus 500 that may beused as either or both of the source device 12 and the destinationdevice 14 from FIG. 1 according to an exemplary embodiment.

A processor 502 in the apparatus 500 can be a central processing unit.Alternatively, the processor 502 can be any other type of device, ormultiple devices, capable of manipulating or processing informationnow-existing or hereafter developed. Although the disclosedimplementations can be practiced with a single processor as shown, e.g.,the processor 502, advantages in speed and efficiency can be achievedusing more than one processor.

A memory 504 in the apparatus 500 can be a read only memory (ROM) deviceor a random access memory (RAM) device in an implementation. Any othersuitable type of storage device can be used as the memory 504. Thememory 504 can include code and data 506 that is accessed by theprocessor 502 using a bus 512. The memory 504 can further include anoperating system 508 and application programs 510, the applicationprograms 510 including at least one program that permits the processor502 to perform the methods described here. For example, the applicationprograms 510 can include applications 1 through N, which further includea video coding application that performs the methods described here.

The apparatus 500 can also include one or more output devices, such as adisplay 518. The display 518 may be, in one example, a touch sensitivedisplay that combines a display with a touch sensitive element that isoperable to sense touch inputs. The display 518 can be coupled to theprocessor 502 via the bus 512.

Although depicted here as a single bus, the bus 512 of the apparatus 500can be composed of multiple buses. Further, the secondary storage 514can be directly coupled to the other components of the apparatus 500 orcan be accessed via a network and can comprise a single integrated unitsuch as a memory card or multiple units such as multiple memory cards.

The apparatus 500 can thus be implemented in a wide variety ofconfigurations.

Precision of MV derived by calculation of intermediate values of motionvectors in affine prediction was increased from ¼ in pixel length to1/16^(th). This increase of precision cause the memory storage capacityfor motion vector field up to 18 bit per motion vector component. Duringvideo codec development each MV was stored with the granularity 4×4pixels. Later few attempts have been made to reduce memory capacity forstoring motion vector information. One of proposals about granularityreduction to the grid size 8×8 was adopted. Another attempt to reduce MVprecision (for temporal MV storage or the local line buffer or both) hasbeen made in [JVET-L0168] by simple removal of MSB (most significantbits) from motion vector component values, which lead to reduction of myrepresenting range which could reduce the efficiency of prediction andcompression of large size pictures and 360° video. Such 16-bitrepresentation of 1/16^(th) precision motion vector is not enough for 8Kor higher resolution video coding. The two other solutions proposes toremove LSB from MV components for both horizontal and vertical directionand it was attempt to remove MSB/LSB adaptively with additional 1 bitfor signaling. The purpose of this disclosure is to provide thesolution/method and a device which may reduce memory capacity in storinginformation for deriving a temporal motion vector prediction withkeeping motion vector representation and precision in reasonable range.Keeping the precision in a reasonable range implies some reduction ofthe precision, resulting in some distortion of the representation.Therefore, a result of the conversion to a floating point representationis a distorted/quantized/rounded value of the MV. Currently availablesolutions operate with 18-bit values of each MV component for storagewith reference frame (FIG. 6 , top). It is lead to memory increase forstoring MVs by 12.5% for HW and by 100% for SW. This disclosure proposesto use 16-bit binary floating point representation of MV componentsvalues for storage within reference frame instead of 18 bits. However,the 16-bit floating point representation is an example and thedisclosure also includes representations with less than 16 bit (a 10 bitrepresentation, for example). Moreover, for the embodiment 1 where MSBare used as exponent part of floating number—there are no change incodec processing in respect to current solution when picture resolutionis small. The basic concept of the disclosure is 16 bit binary floatingpoint representation of MV components values for storage withinreference frame instead of 18 bits. To reduce memory capacity forstoring temporal MVs keeping MV representation and precision inreasonable range. In order to solve the above problems, the followinginventive aspects are disclosed, each of them can be appliedindividually and some of them can be applied in combination:

-   -   1. To use binary floating point representation of MV components        -   method A. The exponent part could be 3 bit, which allows to            have different precision of MV representation from 1/16^(th)            (for MV length up to 256 pixels) to 8 pixels (for MV lengths            up to 32K)        -   method B. Another possible implementation imply 2 bit-for            exponent part, which decrease a bit maximum MV length to 512            (for MV precision 1/16^(th)) and to 8K pixels (for MV            precision equal to 1 pixel)    -   2. Binary floating point representation could be represented in        two possible implementation (3 bits in examples are used for        exponent):        -   method A. Exponent bits in MSB of MV component value FIG. 6            . With following MV restoration operations (for X component            for example):            -   i. shift=MVx>>13            -   ii. Mvx=MVx & 0x01FFF            -   iii. Mvx<<=shift        -   method B. Exponent bits in LSB of MV component value FIG. 7            . With following MV restoration operations (for X component            for example):            -   i. shift=MVx & 0x03            -   ii. Mvx=MVx>>3            -   iii. Mvx<<=shift    -   3. Proposed approach could be used conditionally with indicating        the usage of this mode in SPS/PPS/Slice header/Tile group header        by:        -   method A. The special flag to indicate the usage of floating            point representation or HEVC 16-bit representation of MV        -   method B. the number of bits for exponent part of the MV            value    -   4. Adaptively change the size of exponent depending on:        -   method A. Picture resolution            -   i. If w<2K and h<2K: exp_size is derived as 0 (not                signaled)            -   ii. If w<4K and h<4K: signal one bit for shift value            -   iii. otherwise: signal two bits for shift value        -   method B. signaled in CTU/CU/Block/Unit level exponent size        -   method C. usage within Motion Constrained Tile Sets (MCTS)            -   i. in this case Tile Set size could strongly restrict                the usage of floating point MV representation for small                Tile Set resolution like in aspect 4).a of this                disclosure    -   5. The vertical and horizontal components of MV could have        independent size of exponent portion.    -   6. One of the possible solution where mean value of the vector        component (meanMVx, meanMVy) is removed from the values of the        same component of each MV belonged to the same CTU/CU/Block/Unit        -   method A. The mean value of both components are stored            separately for each CTU/CU/Block/Unit. The MV derived as            MVx=meanMVx+Mvx(i,j), MVy=meanMVy+Mvy(i,j)        -   method B. The mean value of both components are stored in            one of the sub-unit of each CTU/CU/Block/Unit (top-left for            example i=0,j=0). The MV derived as MVx=meanMVx+Mvx(i,j),            MVy=meanMVy+Mvy(i,j) when (i!=0 and j!=0) and            meanMVx=MVx(0,0), meanMVy=MVy(0,0)        -   method C. Where two above solutions (6).a and 6).b) with            meanMVx and meanMVy in following representation:            -   i. Binary floating 16 bit (as solution 1).a)            -   ii. Integer (16 bit)

Furthermore, the disclosure proposes to use 16-bit binary representationof MV components values for storage within reference frame instead of 18bits, wherein 16-bit values can be obtained from the 18-bit values byremoving 2 LSB (least significant bits) or 2 MSB (most significant bits)depending on value signaled in the bitstream. The signaling can be bythe predefined signaling mechanism as described in [JVET-L0168].

To reduce memory capacity for storing temporal MVs keeping MVrepresentation and precision in reasonable range.

In order to solve the above problems, the following inventive aspectsare disclosed, each of them can be applied individually and some of themcan be applied in combination:

-   -   7. Prior to saving MV to the motion buffer, MV components are        converted from 18-bit binary representation to 16-bit        representation, using one of the following methods, depending on        value signaled in bitstream:        -   method A. Removing two LSB by arithmetical right shift by            two (as shown in FIG. 8 )        -   method B. Removing two MSB (for example by clipping to the            range [−2¹⁵,2¹⁵−1]) (as shown in FIG. 9 ).        -   Restoration of MV components (converting from 16-bit to            18-bit binary representation) is performed using following            rules:            -   If method A was used, 18-bit value is obtained from 16                bit value by left arithmetical shift by 2;            -   If method B was used, 18-bit value is obtained from 16                bit value by setting 2 MSB (17-th and 18-th bits) to 0                for positive values or to 1 for the negative values.    -   8. Aspect 7 where 16-bit binary representation is not used for        storing motion information of current picture. In this case MVs        in 16-bit binary representation are used, for example, for TMVP        (temporal motion vector prediction) and/or ATMVP (alternative        temporal motion vector prediction).    -   9. Aspect 8, where method of conversion from 18-bit to 16-bit        binary representation of MV components (method A or method B) is        signaled in bitstream for each frame.    -   10. Aspect 8, where method of conversion from 18-bit to 16-bit        binary representation of MV components (method A or method B) is        signaled in bitstream for each tile.    -   11. Aspect 8, where method of conversion from 18-bit to 16-bit        binary representation of MV components (method A or method B) is        signaled in bitstream for group of tiles.    -   12. Aspect 8, where method of conversion from 18-bit to 16-bit        binary representation of MV components (method A or method B) is        signaled in bitstream for each slice.    -   13. Aspects 7-12, where 18-bit to 16-bit conversional method        (method A or method B) is signaled in SPS/PPS/Slice header/Tile        group header by special flag.    -   14. Aspects 7-8, where method of conversion from 18-bit to        16-bit binary representation of MV components adaptively        selected based on:        -   a. Picture resolution            -   i. If w<2K and h<2K: method B is used (without                signalling)            -   ii. otherwise: signal one bit whether use method A or B        -   b. signaled in CTU/CU/Block/Unit level        -   c. usage within Motion Constrained Tile Sets (MCTS)            -   i. in this case Tile Set size could strongly restrict                the usage of method B for small Tile Set resolution    -   15. The vertical and horizontal components of MV could have        independent signaling.

FIG. 10 shows a flow diagram of a general motion vector compressionmethod according to the disclosure. The method comprises operation 101of obtaining a temporal motion vector; operation 102 of determining acompressed motion vector using a binary representation of the temporalmotion vector, wherein the binary representation comprises an exponentpart and/or a mantissa part, and wherein the exponent part comprises Nbits, the mantissa part comprises M bits, and wherein N is anon-negative integer and M is a positive integer; and operation 103 ofperforming a temporal motion vector prediction (TMVP) using thecompressed motion vector.

Although embodiments of the application have been primarily describedbased on video coding, it should be noted that embodiments of the codingsystem 10, encoder 20 and decoder 30 (and correspondingly the system 10)and the other embodiments described herein may also be configured forstill picture processing or coding, i.e. the processing or coding of anindividual picture independent of any preceding or consecutive pictureas in video coding. In general only inter-prediction units 244 (encoder)and 344 (decoder) may not be available in case the picture processingcoding is limited to a single picture 17. All other functionalities(also referred to as tools or technologies) of the video encoder 20 andvideo decoder 30 may equally be used for still picture processing, e.g.residual calculation 204/304, transform 206, quantization 208, inversequantization 210/310, (inverse) transform 212/312, partitioning 262/362,intra-prediction 254/354, and/or loop filtering 220, 320, and entropycoding 270 and entropy decoding 304.

Embodiments, e.g. of the encoder 20 and the decoder 30, and functionsdescribed herein, e.g. with reference to the encoder 20 and the decoder30, may be implemented in hardware, software, firmware, or anycombination thereof. If implemented in software, the functions may bestored on a computer-readable medium or transmitted over communicationmedia as one or more instructions or code and executed by ahardware-based processing unit. Computer-readable media may includecomputer-readable storage media, which corresponds to a tangible mediumsuch as data storage media, or communication media including any mediumthat facilitates transfer of a computer program from one place toanother, e.g., according to a communication protocol. In this manner,computer-readable media generally may correspond to (1) tangiblecomputer-readable storage media which is non-transitory or (2) acommunication medium such as a signal or carrier wave. Data storagemedia may be any available media that can be accessed by one or morecomputers or one or more processors to retrieve instructions, codeand/or data structures for implementation of the techniques described inthis disclosure. A computer program product may include acomputer-readable medium.

By way of example, and not limiting, such computer-readable storagemedia can comprise RAM, ROM, EEPROM, CD-ROM or other optical diskstorage, magnetic disk storage, or other magnetic storage devices, flashmemory, or any other medium that can be used to store desired programcode in the form of instructions or data structures and that can beaccessed by a computer. Also, any connection is properly termed acomputer-readable medium. For example, if instructions are transmittedfrom a website, server, or other remote source using a coaxial cable,fiber optic cable, twisted pair, digital subscriber line (DSL), orwireless technologies such as infrared, radio, and microwave, then thecoaxial cable, fiber optic cable, twisted pair, DSL, or wirelesstechnologies such as infrared, radio, and microwave are included in thedefinition of medium. It should be understood, however, thatcomputer-readable storage media and data storage media do not includeconnections, carrier waves, signals, or other transitory media, but areinstead directed to non-transitory, tangible storage media. Disk anddisc, as used herein, includes compact disc (CD), laser disc, opticaldisc, digital versatile disc (DVD), floppy disk and Blu-ray disc, wheredisks usually reproduce data magnetically, while discs reproduce dataoptically with lasers. Combinations of the above should also be includedwithin the scope of computer-readable media.

Instructions may be executed by one or more processors, such as one ormore digital signal processors (DSPs), general purpose microprocessors,application specific integrated circuits (ASICs), field programmablelogic arrays (FPGAs), or other equivalent integrated or discrete logiccircuitry. Accordingly, the term “processor,” as used herein may referto any of the foregoing structure or any other structure suitable forimplementation of the techniques described herein. In addition, in someaspects, the functionality described herein may be provided withindedicated hardware and/or software modules configured for encoding anddecoding, or incorporated in a combined codec. Also, the techniquescould be fully implemented in one or more circuits or logic elements.

The techniques of this disclosure may be implemented in a wide varietyof devices or apparatuses, including a wireless handset, an integratedcircuit (IC) or a set of ICs (e.g., a chip set). Various components,modules, or units are described in this disclosure to emphasizefunctional aspects of devices configured to perform the disclosedtechniques, but do not necessarily require realization by differenthardware units. Rather, as described above, various units may becombined in a codec hardware unit or provided by a collection ofinteroperative hardware units, including one or more processors asdescribed above, in conjunction with suitable software and/or firmware.

For reference, the following logical operators are defined as follows:

-   -   x && y Boolean logical “and” of x and y    -   x∥y Boolean logical “or” of x and y    -   ! Boolean logical “not”    -   x?y:z If x is TRUE or not equal to 0, evaluates to the value of        y; otherwise, evaluates to the value of z.

For reference, the following relational operators are defined asfollows:

-   -   > Greater than    -   >= Greater than or equal to    -   < Less than    -   <= Less than or equal to    -   == Equal to    -   != Not equal to

When a relational operator is applied to a syntax element or variablethat has been assigned the value “na” (not applicable), the value “na”is treated as a distinct value for the syntax element or variable. Thevalue “na” is considered not to be equal to any other value.

For reference, the following bit-wise operators are defined as follows:

& Bit-wise “and”. When operating on integer arguments, operates on atwo's complement representation of the integer value. When operating ona binary argument that contains fewer bits than another argument, theshorter argument is extended by adding more significant bits equal to 0.

| Bit-wise “or”. When operating on integer arguments, operates on atwo's complement representation of the integer value. When operating ona binary argument that contains fewer bits than another argument, theshorter argument is extended by adding more significant bits equal to 0.

{circumflex over ( )} Bit-wise “exclusive or”. When operating on integerarguments, operates on a two's complement representation of the integervalue. When operating on a binary argument that contains fewer bits thananother argument, the shorter argument is extended by adding moresignificant bits equal to 0.

x>>y Arithmetic right shift of a two's complement integer representationof x by y binary digits. This function is defined only for non-negativeinteger values of y. Bits shifted into the most significant bits (MSBs)as a result of the right shift have a value equal to the MSB of x priorto the shift operation.

x<<y Arithmetic left shift of a two's complement integer representationof x by y binary digits. This function is defined only for non-negativeinteger values of y. Bits shifted into the least significant bits (LSBs)as a result of the left shift have a value equal to 0.

In summary, the present disclosure provides a motion vector compressionmethod, comprising: obtaining a temporal motion vector; determining acompressed motion vector using a binary representation of the temporalmotion vector comprising an exponent part and/or a mantissa part,wherein the exponent part comprises N bits, the mantissa part comprisesM bits, and wherein N is a non-negative integer and M is a positiveinteger; and performing a temporal motion vector prediction (TMVP) usingthe compressed motion vector.

1. A motion vector compression method, comprising: obtaining an 18 bittemporal motion vector; determining a compressed motion vector of the 18bit temporal motion vector when an indicator indicates the 18 bittemporal motion vector need to be compressed, wherein a binaryrepresentation of the compressed motion vector comprising an exponentpart or a mantissa part, wherein the exponent part comprises N bits, themantissa part comprises M bits, wherein N is a non-negative integer andM is a positive integer, and wherein the representation of thecompressed motion vector is 10 bits; and performing a temporal motionvector prediction (TMVP) using the compressed motion vector.
 2. Themotion vector compression method of claim 1, wherein the exponent partcorresponds to most significant bit(s) (MSB) of the binaryrepresentation and the mantissa part corresponds to least significantbit(s) (LSB) of the binary representation; or, the exponent partcorresponds to LSB of the binary representation and the mantissa partcorresponds to MSB of the binary representation.
 3. The motion vectorcompression method of claim 2, further comprising: when the exponentpart corresponds to MSB of the binary representation and the mantissapart corresponds to LSB of the binary representation, deriving a valueof the compressed motion vector by: deriving a first shift value byapplying a right shift of M bit to the binary representation; derivinglast M bit of the binary representation as a first basic binaryrepresentation; and deriving the value of the compressed motion vectorby applying a left shift of the first shift value to the first basicbinary representation.
 4. The motion vector compression method of claim2, further comprising: when the exponent part corresponds to LSB of thebinary representation and the mantissa part corresponds to MSB of thebinary representation, deriving a value of a motion vector component by:deriving last N bit of the binary representation as a second shiftvalue; deriving a second basic binary representation by applying a rightshift of N bit to the binary representation; and deriving the value ofthe compressed motion vector by applying a left shift of the secondshift value to the second basic binary representation.
 5. The motionvector compression method of claim 1, wherein the 18 bit temporal motionvector comprises a motion vector horizontal component and a motionvector vertical component.
 6. A non-transitory computer-readable storagemedium storing executable instructions for execution by a processingcircuitry, wherein the executable instructions, when executed by theprocessing circuitry, configures the processing circuitry to carry outthe method according to claim
 1. 7. A decoder, comprising: circuitryconfigured to perform the method of claim
 1. 8. A video data decodingdevice, comprising: a non-transitory memory storage, configured to storevideo data in a form of a bitstream; and a video decoder, configured toperform the method according to claim
 1. 9. A encoder, comprising:circuitry configured to perform the method of claim
 1. 10. A video dataencoding device, comprising: a non-transitory memory storage, configuredto store video data in a form of a bitstream; and a video decoder,configured to perform the method according to claim
 1. 11. Anon-transitory storage medium storing a bitstream and one or moreinstructions executable by at least one processor to perform operationsof encoding or decoding of the bitstream, the operations comprising:obtaining an 18 bit temporal motion vector; determining a compressedmotion vector of the 18 bit temporal motion vector when an indicatorindicates the 18 bit temporal motion vector need to be compressed,wherein a binary representation of the compressed motion vectorcomprising an exponent part or a mantissa part, wherein the exponentpart comprises N bits, the mantissa part comprises M bits, wherein N isa non-negative integer and M is a positive integer, and wherein therepresentation of the compressed motion vector is 10 bits; andperforming a temporal motion vector prediction (TMVP) using thecompressed motion vector.
 12. The storage medium of claim 11, whereinthe exponent part corresponds to most significant bit(s) (MSB) of thebinary representation and the mantissa part corresponds to leastsignificant bit(s) (LSB) of the binary representation; or, the exponentpart corresponds to LSB of the binary representation and the mantissapart corresponds to MSB of the binary representation.
 13. The storagemedium of claim 12, wherein the operations further comprise: when theexponent part corresponds to MSB of the binary representation and themantissa part corresponds to LSB of the binary representation, derivinga value of the compressed motion vector by: deriving a first shift valueby applying a right shift of M bit to the binary representation;deriving last M bit of the binary representation as a first basic binaryrepresentation; and deriving the value of the compressed motion vectorby applying a left shift of the first shift value to the first basicbinary representation.
 14. The storage medium of claim 12, wherein theoperations further comprise: when the exponent part corresponds to LSBof the binary representation and the mantissa part corresponds to MSB ofthe binary representation, deriving a value of a motion vector componentby: deriving last N bit of the binary representation as a second shiftvalue; deriving a second basic binary representation by applying a rightshift of N bit to the binary representation; and deriving the value ofthe compressed motion vector by applying a left shift of the secondshift value to the second basic binary representation.
 15. The storagemedium of claim 11, wherein the 18 bit temporal motion vector comprisesa motion vector horizontal component and a motion vector verticalcomponent.